Replicated, weakly consistent databases are well suited for applications involving the sharing if data among multiple users with low speed or intermittent communication links. As an example, these applications can run in a mobile computing environment that includes portable machines with less than ideal network connectivity. A user's computer may have a wireless communication device, such as a cell modem or packet radio transceiver relying on a network infrastructure that may suffer from not being universally available and/or from being very expensive. Such a computer may use short-range line-of-sight communication, such as the infrared "beaming" ports available on some commercial personal digital assistants (PDAs). Alternatively, the computer may have a conventional modem requiring it to be physically connected to a phone line when sending and receiving data, or it may only be able to communicate with the rest of the system when inserted in a docking station. Indeed, the computer's only communication device may be a diskette that is transported between machines by humans. Accordingly, it will be apparent that a mobile computer may experience extended and sometimes involuntary disconnection from many or all of the other devices with which it wants to share data.
In practice, mobile users may want to share their appointment calendars, bibliographic databases, meeting notes, evolving design documents, news bulletin boards, and other types of data in spite of their intermittent network connectivity. Thus, there is a need for systems that enable mobile clients to actively read and write shared data. Even though such a system most probably will have to cope with both voluntary and involuntary communication outages, it should behave from the user's viewpoint, to the extent possible, like a centralized, highly-available database service.